1. Field of the Invention
The present invention relates to a hydrogen storage material and a hydrogen storage apparatus which can absorb-desorb hydrogen.
2. Description of the Related Arts
Hydrogen energy is expected to be used in, for example, beginning with fuel cells used in electric sources for electric automobiles, a variety of applications. In order to put hydrogen energy to practical use, technology for safely storing-transporting hydrogen becomes important. As technologies for storing hydrogen, for instance, there are methods of compressing hydrogen with a high pressure, or liquefying it at a low temperature and filling it in a container, such as a bomb. However, in the method of compressing it with a high pressure, in case of storing a practical amount of hydrogen, its container volume has enlarged. Moreover, in the method of liquefying it at a low temperature, since it is necessary to cool hydrogen to 20 K or less, in addition, since it is necessary to always cool the container, it has a disadvantage in that the costs therefor have enlarged.
On the other hand, there is a method of storing hydrogen by filling a material, which can absorb-desorb hydrogen, in a container and storing hydrogen in the material. As one of hydrogen storage materials which can absorb-desorb hydrogen, for example, it is possible to name hydrogen absorbing alloys which absorb gaseous hydrogen in the form of solid, being metallic hydrides, under predetermined conditions and desorb hydrogen under the other conditions. Moreover, as another hydrogen storage material, porous carbon materials attract attention which absorb hydrogen by adsorbing it.
However, hydrogen absorbing alloys are heavy, and the hydrogen storage capacities per unit weight are small. Moreover, since the exothermic-endothermic heat quantities in absorbing-desorbing hydrogen are large, it is necessary to accompany cooling facilities and the like with the container filled therewith. Moreover, rare-earth-based alloys and so forth, being the representative examples of hydrogen absorbing alloys, include rare metals, and accordingly it is difficult to secure the resources and the costs are high. On the other hand, porous carbon materials have an advantage in that they are abundant as resources and are lightweight. However, porous carbon materials are such that the bulk densities are low generally, and, in case of using them by filling them in a container, it is not possible to say that the hydrogen storage capacities per unit volume is sufficient. In addition, since the hydrogen storage capacities at ordinary temperature are small, in order to obtain a practical hydrogen storage capacity, it is inevitable to use them at a low temperature of from −30° C. to −70° C. approximately.
The present invention has been done in view of the aforementioned circumstances, and its assignment is to provide a hydrogen storage material whose hydrogen storage capacity per unit volume is large, in addition to being less expensive relatively and lightweight. Further, its assignment is to provide a hydrogen storage material whose hydrogen storage capacity is large at ordinary temperature. Furthermore, its assignment is to provide a hydrogen storage apparatus whose hydrogen storage capacity per unit volume is large.